The prior art contains teachings pertaining to electrically operated levels including illuminating elements to indicate angular deviations and mercury switch means to activate the illuminating elements. In the prior art, where mercury is employed in the electrical circuits, a rather large pool of mercury is utilized to make contact with electrical terminals of light bulbs during angular deviations of the instrument. Such an arrangement is shown in U.S. Pat. No. 1,375,278. Such large pools of mercury do not contribute to the making of a precision level and the mercury pool has a tendency, particularly when vibration is present, to make contact with the terminals of more than one indicator light bulb at a time. The prior art construction is also rather expensive and somewhat complicated.
Another prior art arrangement in U.S. Pat. No. 4,079,521 utilizes liquid contact switching means contained within rotatable mounting discs which must be machined or molded with precision, rendering the resulting level quite expensive and difficult to manufacture.
Accordingly, the objective of this invention is to provide a precision illuminated level employing inexpensive state-of-the-art solid state illuminating elements connected in a battery-powered circuit through a small droplet of mercury which can make contact sequentially with leads of the light emitting elements as the position of the level deviates from the true horizontal or true vertical. The leads of the light emitting elements are positioned with precision along an arcuate path along which the mercury droplet travels. A single on-off switch is employed to power the light emitting elements of the level during use in a horizontal or vertical mode. The body portion of the level lends itself to molding with high impact plastics. The instrument is convenient to use, rugged and durable, precise and reliable in operation, and comparatively inexpensive to manufacture, utilizing mass production techniques. It can be manufactured in a variety of sizes.
Other features and advantages of the invention will become apparent during the course of the following detailed description.